Distinct downstream effectors downstream of InR activity control multiple aspects of oogenesis.
Authors: Tancia Bradshaw; Alissa Armstrong
Affiliation: University of South Carolina
Keywords: b. oogenesis; b. germline stem cell
Approximately 40% of adults in the United States are obese. Adipocytes, the primary cellular component of fat tissue, are nutrient-sensitive and secrete adipokines that control physiology, including metabolism, appetite, and insulin sensitivity. Despite the intricate relationship between dietary input, adipose tissue, and peripheral organ function, we are at the tip of the iceberg regarding our understanding of the cellular and molecular mechanisms underlying adipose communication to other tissues. The Drosophila ovary receives nutritional signals from the fat body with multiple nutrient-sensing pathways functioning in adipocytes to control oogenesis. Insulin/insulin-like growth factor signaling (IIS) within adult adipocytes remotely controls oocyte production at distinct stages of oogenesis. The PI3K/Akt1 axis in adipocytes promotes germline stem cell (GSC) maintenance via SGG, Drosophila GSK3beta, yet its targets in this context remain to be identified. Here, we measured the expression of candidate SGG/GSK3beta substrates in adipocytes and assessed their role in regulating GSC number. Using the UAS/Gal4 system for adipocyte-specific knockdown of four putative targets, ATPCL, chb, porin, and SREBP, we find that SREBP acts within adipocytes to regulate GSC maintenance. In addition, we find that a second axis downstream of the insulin receptor, the Ras/MAPK signaling pathway, acts cell autonomously to control adipocyte size and remotely to regulate the survival of early and late germline stem cell progeny – germline cysts and vitellogenic egg chambers, respectively. Future studies will identify how SREBP activity within adipocytes controls GSC maintenance as well as additional SGG/GSK3beta substrates within adipocytes required to communicate to the ovary. These studies highlight the complex mechanisms that underlie inter-organ communication.